The concept of non-impacting linear vibrators is known in the art, typically, a cylindrical mass oscillates back and forth in a cylindrical chamber as air flows into and out of the cylindrical chamber. The vibrators are generally lubrication free since air is used to support the cylindrical mass as it oscillates back and forth. If lubricants such as oils or the like are used it results in an oil mist being discharged into the atmosphere. While such systems provide vibration one of the difficulties with such systems is that the vibrators do not always start on-demand. That is, as air or other fluid is introduced into the cylindrical chamber the air might pass around the cylindrical mass without inducing the required oscillation of the mass therein.
In one embodiment of the known linear vibrators the vibrator includes a cylindrical shaped piston that is driven back and forth in a chamber by air that simultaneously pushes the piston back and forth as it forms an air bearing around the piston to provide essentially a frictionless surface between the piston and the housing. One of the drawbacks of such vibrators is that to ensure that the vibrator responds to the introduction of the fluid into the housing it is usually necessary to have some mechanical means such as a spring to bias the piston to facilitate initiation of the oscillating activity of the piston. That is, when fluid such as air is introduced into the chamber the piston, which is to be supported by an air bearing, might not immediately begin oscillating when air is introduced into the chamber. Consequently, if one wants to ensure start-up one needs to initiate the oscillating action of the piston through incorporating a mechanical device such as a spring or the like in the vibrator. However, introducing mechanical start-up devices such as springs reduces the life of the vibrator since the springs eventuality break through metal fatigue.
The present invention in one embodiment provides an on-demand linear vibrator with immediate start-up that avoids the problems of lubrication contamination as well as the problem of breakdown due to fatigue of a start-up mechanism. In another embodiment the on-demand linear vibrator with immediate start-up includes redundant on-demand start-up systems.